See also

This script demonstrates one method of doing automatic failover using the Netwatch function and using scripting to enable or disable gateways. This is probably not the most efficient way, but it works. I would welcome any input on how it can be improved.

The situation:

You have 2 lines going out to the internet - 10.0.0.12 and 10.0.0.13. You have setup a mangle to mark HTTP traffic (optional) and want to route http along the 2 lines using load balancing.

Now you have ECMP for HTTP only. This is nice because MSN messenger, banking websites and other programs and problem sites will not be broken in the same way it might be if you used ECMP for all protocols.

What I then do is for example mark SMTP traffic and route this out through 10.0.0.12:

Then I need to setup 2 routes to specific addresses to force the router through specific gateways to "test" the links. These should not be popular addresses with your users! Otherwise when a gateway goes down they will have no access to those sites. The addresses I am using as an example are 1.1.1.12 to test 10.0.0.12, and 1.1.1.13 to test 10.0.0.13.

Next I use the Netwatch Function to switch all traffic to the working gateway should any of the gateways fail: